Production of motor fuel



F. E. FREY PRODUCTION 0F MOTOR FUEL Aug. 24, 1943.

Filed Oct. 2. 1939 `ular weights.

Patented Aug. 24, 1943 PRODUCTION OF MOTOR FUEL Frederick E. Frey, Bartlesville, Okla., assignor `to Phillips Petroleum Company, a corporation oi Delaware Application October 2, 1939, Serial No. 297,600

3 Claims.

This invention relates to the production or manufacture of motor fuel from low boiling hydrocarbons, and more particularly to the production of hydrocarbons in the gasoline boiling range suitable for premium motor fuels from paran hydrocarbons having three to ve carbon atoms per molecule.

Marly processes have been proposed for converting normally gaseous hydrocarbons into hydrocarbons having higher molecular Weights, such as motor fuels and lubricants. Some of these processes are dependent upon having olefin hydrocarbons present in large proportions in the charge stock, such `asin Well-known thermal and catalytic polymerization processes for producing motor fuel from refinery gasesl containing unsaturated components from cracking stills. Still other processes are adapted to produce motor fuel from normally gaseous paraflins, such as unitary thermal conversion processes, or multistage process employing a dehydrogenation step as a iirst part of the process, followed by a conversion of olei'lns so produced. Still other processes have been proposed wherein a paraffinic hydrocarbon stream and an olenic hydrocarbon stream are charged toa process, and the parains and olens are caused to interreact, or as it is generally stated, the parains are alkylated by the olens to form parans having higher molec- The process of the present invention involves a cooperation between a polymerization step, for the production of motor fuel range hydrocarbons by the polymerization of lighter olens, and an alkylation step, for the production of motor fuel range hydrocarbons by the alkylation of lighter parains with olelins which may be heavier and/or lighter than the final product. The polymerization step is preferably one carried out with the aid of a solid polymerization catalyst, such as silica-alumina or the like, solid phosphoric acid, acidl copper phosphate, or the like; and the alkylation step is preferably carried out in the presence `of concentrated sulfuric acid,

using olens which have been recovered from the eiliuent of the polymerization step. It has been found that the paraflins charged to the alkylation step should be isoparafns such as isobutane (Z-methyl propane) or isopentane (2- methyl butane) or the like, and such maybe separated from the unreacted hydrocarbons which have passed through the polymerization step, or may befindependently introduced to the process as a separate charge to the acid alkylation step.

'superior in these respects.

In one particular manner of practicing my'invention, isobutane is thermally dehydrogenated forming propene and isobutene, and hydrogen and methane are removed from the effluent. A fraction consisting of hydrocarbons having three and more carbon atoms perfmolecule and comprising predominantly propene, isobutene and isobutane is passed at an elevated pressure over a solid polymerization catalyst under conditions such that essentially all of the isobutene is polymerized along with a substantial portion of the propene, forming polymers inthe gasoline boiling range. Under optimum conditions, considerable amounts of isoheptenes and isooctenes are formed, and the polymerization effluent also contains higher boiling olefinic polymers and some unreacted propene. In this particular case the mat-erial which is lower boiling than isobutane contains a large portion of propene and is readily separated from the polymerization eiliuent by-fractional distillation in a vdepropanizer. Likewise, the higher boiling oleiinic polymers are readily separated from the gasoline range polymers. Either, or both, oi' these oleflnic fractions constitute a Valuable part, of the charge to the acid alkylation step. In this particularlinstance the unreacted paraflins in the polymerization effluent are predominantly isobutane, and a portion of such a fraction may constitute the paraftinic portion of the hydrocarbon charge to the acid alkylation step. This fraction will contain a small amount of unreacted isobutene which willalso undergo a desirable reaction in the alkylation step. Isopentane may be blended with the isobutane fraction charged to the alkylation step or may constitute the entire isoparaflinic portion of the charge, or isobutane from some other source may be charged to the alkylation step. Even when higher boiling olenic polymers are the sole olenic charge to the acid alkylation, the alkylatlon products will be isoparalins in the gasoline boiling range, since it appears that such high boiling polymers undergo concomitant scission reactions, substantially all of the fragments being oleflnic and taking part in the reaction, rather than that these higher boiling olens join directly to the chargedisoparan to form still higher boiling products. The gasoline boiling range isoparains have high antidetonating qualities and octane numbers, and the olen polymers in the gasoline boiling range are also These gasoline products may be used separately as motor fuels or blending stocks, Athe olefin polymer may be hydrogenated before use; or these fractions may be blended together to form a premium motor fuel. In those cases where an olcnic motor fuel is not undesirable, this latter procedure is es` pecially effective, since the oleflns have "blending" octane numbers even higher than their straight octane numbers in the pure state, and to blend them with isoparaflins gives a still more superior result.

While the'catalytic polymerization produces a polymer which has a superior octane number, both as it is and after hydrogenation to form a paramnlc material, it fails to convert all of the ole- ;ns charged and generally also produces a certain amount of polymer which may be undesirably heavy. Although catalytic alkylation of hydrocarbon material to give a product in the same boiling range produces a paraffinic product directly which also has a superior octane number, the octane number will generally not be quite as high as that of the former product resulting from polymerization.

The cooperative combina-tion of the present invention not only gives a total lproduct with a high octane number, but also depletes the olefin content of the hydrocarbon stream produced by dehydrogenation and charged to the alkylation step, and thus aids in producing a desirable alkymer by raising the ratio of paraffin to olefin in this stream and facilitates control of this reaction. Thus, the combination gives a total product having an octane number higher than could be produced by alkylation alone, and also results in a better utilization of olefin hydrocarbons and production of isoaliphatic hydrocarbons in the gasoline range than would result from catalytic polymerization alone.

It is an object of my invention to produce a premium liquid motor fuel from normally gaseous hydrocarbons.

Another object of this invention is to provide a process for the production of gasoline boiling range hydrocarbons from normally gaseous hydrocarbonsV by a combination of an olen D013?- merization step and an olefin-paraflin alkylation step.

A further object. of this invention is to form polymers in the gasoline range from lighter olens, and to form isoparains in the gasoline range from lighter isoparaihnsand unreacted and overreaeted olens from the effluent containing the aforesaid gasoline range polymers.

Further objects and advantages will become aP- parent from the accompanying disclosure and discussion.

Reference will now be made to the drawing which forms a part of this specification and which shows diagrammatically one arrangement of apparatus for practicing my invention.

A low boiling saturated hydrocarbon material, such as a butane fraction of natural gas containing a high concentration of isobutane, enters the system through pipe I and valve II and is passed by pump I2 through the coil I3 in the dehydrogenating furnace I4. In many cases where such a hydrocarbon stream comes directly from a fractional distillation process or from some other separation step it may be under a pressure sufficiently high to obviate the necessity of the pump I2 and in such a case, of course, the pump may Vbe omitted. The dehydrogenation which takes place in the unit represented by the coil I3 and the furnace I4 may be of any type of dehydrogenation process known to the art and may be either thermal or catalytic or a combination of both. The pressure will generally not be in excess of about 200 pounds per square inch, and preferably will be lower; andV the temper-af ture will be between 850 and 1250 F.

' From the dehydrogenation furnace I4 the ellluent passes through cooler I5, pump or compressor I6 and cooler and condenser I1 to separating means represented by the fractionating column 20, supplied with heating means 2| at the bottom and cooling means 22 at the top. Hy' drogen and any light hydrocarbons formed in the dehydrogenation are removed from the system through pipel 23 and valve 24; and any heavy hydrocarbons, tar and/or carbon may be removed from the system through pipe 25 and valve 26. This separation may be aided by the use o1' cooled, unreacted hydrocarbon `(which may be flashed to provide direct vaporization and refrigeration as has been more fully described by Hays et al. in their copending application Serial No. 336,250, filed May 20, 1940), introduced through pipe 19 and expansion valve 80. A hydrocarbon stream, comprising unreacted parafllns and olens produced by the dehydrogenation, passes from the separating mean's 20 through pipe 21 and valve 28, and is passed at'a suitable polymerization pressure, preferably between 200 and 2000 pounds per square inch, by pump 29 through pipe 30. heater 3l and pipe 32 to the polymerization unit 33. Normally gaseous unsaturated hydrocarbons, such as propylene and/or butenes as'may be recovered from an oil cracking process. may be introduced through pipe 34 and valve 35, and such'a stream may constitute the only hydrocarbon material charged to this part of the process. In such a case the dehydrogenation part of the system just described may not be used. or may be used only to dehydrogenate parain hydrocarbons in the stream entering through pipe 34 which pass through the polymerization system and are ultimately passed through pipe 63 to the pipe I0.

The polymerization carried out in unit 33 will preferably be a catalytic polymerization rather than a thermal one and may be carried out with any known polymerization catalyst which promotes the formation of simple, low boiling polymers from light olefins such as propylene and/or butylenes. Such catalysts may be silica-alumina, solid phosphoric acid, diluted aqueous solutions of liquid acids such as sulfuric acid, or the like. 1f the hydrocarbon stream charged to this polymerization step contains two or more species of oleiins such as the mixture of propylene and isobutene which results from the thermal dehydrogenation of isobutane, the unit may be so operated as to secure interpolymerization of these olens, one such method being described in Frey's copending application Serial No. 294,377, filed September 11, 1939.

The polymerization eilluent passes through pipe 3l and valve 38 to separating means represented by the fractionating column 40, supplied with a heating coil 4I at the bottom and a cooling coil 42 at the top. The entire polymer fraction, comprising olen polymers boiling in the motor fuel range and also higher boiling polymers, passes from the bottom of means 40 through pipe 43 and Valve 44 to fractionating column 45, wherein a separation is made between light polymers suitable for motor fuel or as a motor fuel blending stock which is removed from the system through Pipe 46 and valve 41, and heavier polymers which may be removed through pipe 48 and valve 49.

50 and valve 5|.

Extremely heavy polymers or tar and the like may be removed from the system through pipe Separation and fractionation in the column 45 is aided by heating coil 52 in 'the bottom and cooling coil 53 in the top.

-Light hydrocarbons which have passed through the polymerization step unaffected, including -parafn hydrocarbons along with unreacted olefins, pass from the means 40 through pipe 55 and A valve 56 to the fractionator 60, wherein a separation is made between lighter unreactedhydrocarbons and heavier unreacted hydrocarbons, the separation being aided by aheating means 6| and cooling means 62. ,Heavier unreacted. hydrocarbons, which will be substantially entirely parans, pass from the bottom of fractionator 60 through pipe 63 controlled by a valve 64, and may be passed through valve 65 to pipe I0 and the dehydrogenation step, or any part or all of this stream may be withdrawn from the system through pipe 66 andvalve 61. A stream of light unreacted hydrocarbons, which Will contain the majority of the unreacted olefins, is removed from the top ofv fractionator 60 through pipe 10, and part or all of the stream may be removed through valve 1| when it is not possible or desirable to take care ofthis stream by the methods Y to be hereinafter described, or when the content of parailns is sufficiently high to warrant a discard of a part of this stream or to warrant a separation of paraffins from olens in apparatus not shown, with subsequent reintroduction to the process of either one `or both of these fractions as will be readily appreciated. A portion of the olefin-containing stream passing through pipe 10 may be diverted through pipe l2 and valve 13 and returned to the polymerization step by pump This may be done by addition of this stream through pipe 15,'and valve 16 directly to pipe 30. or by passing a part or all of the stream through pipe 11, cooler 18, pipe 19 and valve 804 as a refrigerating agent to the top of the fractionator 20, as previously mentioned. Alternatively, or concomitantly, a portion of the stream passing through pipe 10 may be passed through pipe 85 and valve 86 to the sulfuric acid alkylation step to be more fully hereinafter discussed. When the charge to the polymerization step contains appreciable amounts of both propylene and butanes, or when a propane-lontane mixture is dehydrogenated or when a renery C3-C4 fraction is directly charged, or when isooutane is thermally dehydrogenated, the stream passing from fractionator 60 through pipe 63 will contain .predominantly paraiiin hydrocarbons such as butanes, while the stream passing from this fractionator through pipe 10 will contain the major part of the unpolymerized olens, mainly propene, at least a part of which can conveniently be recycled to the polymerization step. If the polymerization step has been so conducted that practically all of the olefin material charged has undergone polymerization, the stream passing `through pipe 55 may be passed directly to pipe 63 through pipe 58 and valve 59, with suitable controlof valves l56land 64.

As has been previously discussed, it is an object of this invention to react olens, which are present in the'polymerization eilluent and which are unsuitable by reason of their boiling range or molecular Weight for direct inclusion in motor fuel, with isoparains in the presence of a suitable agent, such as concentrated sulfuric acid, to form further quantities of hydrocarbons in the motor fuel range. When the polymerization is so conducted that substantially al1 the light oleflns charged are polymerized, the only oleiins unsuitable for motor fuel will have high molecular weights, but generally the polymerization conditions Will not be so drastic and both light and heavy oleiins can be sent to the acid alkylation step and reacted there, and a process involving this modification is also a part of my invention.

Heavy olens are passed from pipe 48 through pump |00, pipe |0| and valve |02 tothe alkylation process, and light olefins are passed from pipe 85 through pump |03, pipe |04 and valve |05 to the alkylation process. A hydrocarbon stream consisting of or comprising large quantities of isoparans such as isobutane and/or isopentane is passed through pump |01 and pipe |08 to the alkylation process. If a large part of the paraffin hydrocarbons in the eiluent of the polymerization step are isoparaffins, such as isobutane or isopentane, this isoparafin charge may comprise or consist of a portion of the stream passing through pipe 63, which is passed through pipe ||0 and valve to pump |01. If such is not the case, or if additional isoparaflin charge is needed, isoparains ymay be introduced through pipe ||2 and valve ||3 into pipe H0. Light olens separated fromk the stream discharged through valve 1| and in a more concentrated iorm may also be introduced through pipe Hz, or through pipe 81 and valve 88 into pipe 85.

A suitable alkylating agent, such as concentrated sulfuric acid, is charged to the process through pipe ||5, valve ||6, pump ||1 and pipe ||8, which in this case leads into pipe |08. As one method of performing the alkylation, the isoparafns, olens and sulfuric acid may be rapidly and intimately mixed at the juncture of pipes |08 and ||8, and the, mixture is. rapidly passed through the tube coil |20 in the reactor-heatexchanger |2|. Since the alkylation reaction is exothermic and is adversely affected by reaction temperature in excess of about 80 .to 100 F., it is preferable that this initial part of the reaction should be carried out with a removal of heat suiiicient to maintain a desired operating temperature. A tube coil of a type similar to that used in tube stillseffects a turbulent mixing of the material passing through it, and thus contributes to the eiiiciency` of the alkylation reaction. 'I'his reaction may be continued vand completed in an enlarged chamber |22,` which may be insulated and which affords an extended reaction time to the mixture Without much mixing or turbulence. It may at times be desirable to have a part or all of the light oleflns enter the alkylatioii system at some intermediate point or points, and in such an event this may be accomplished by passing any desired portion of the stream from pipe |04 through one or more pipes illustrated by pipe H9, controlled by a valve |29, to one or more intermediate points of the coil |20, with suitable control of valve |05. From the chamber |22 the mixture, substantially completely reacted, passes through pipe |23 to a separator |24, wherein a separation takes place between the hydrocarbon material and the sulfurie acid phase. This latter is removed through pipe |25, and may be removed from the system through Valve |26, or any part or all of it may be passed through pipe |21 and valve |28 to pipe ||5 to be used again in the process.

The hydrocarbon material, containing the products'of the alkylation along with unreacted throughpipe and valve |3I. It will generally be desirable to eiect an intimate contact of this hydrocarbon material with an acid-neutralizing agent such as sodium hydroxide or carbonate or the like, and such material as an aqueous solution or a slurry in some hydrocarbonmiscible material can be introduced through pipe |32 and valve |33 and the combined mixture passed to separator |34. Anyexcess neutralizing agent and products of the neutralization are removed, as through pipe |35 and valve |36, while hydrocarbon material is passed `through pipel |31, valve |38, and through pump |39 to hydrocarbon separating means illustrated by the fractionator |40 which is equipped with a heating coil |4| at the bottom and a cooling coil |42 at the top. A hydrocarbon fraction comprising a large proportion of hydrocarbons in the motor kfuel boiling range produced by the alkylation, or

blending stock, or may be subjected to further fractionationv to recover certain` narrow boiling fractions of simple composition comprising certain highly desirable individual hydrocarbons. Heavier hydrocarbons are removed from a lower point of the fractionator through pipe and may be discharged from the system through valve |46. This fraction may at times contain y an appreciable proportion of higher boiling olefin polymers, suitable forl reaction 'in the acid alkylation step. In such cases, a portion of the stream may be passed from pipe |45 through pipe |41 and valve |48 to pipe 48, where it is mixed with the heavy polymer passing from the polymerization step to the alkylation step.

A hydrocarbon stream lighter thanr the alkymer, and comprising low-boiling unreacted isoparailins, is removed from an upper part of the iractionator |40 through pipe |50, and may be passed through va1ve|5|, pump |52 and pipe- |53 to pipe ||0 for further passage 'through the alkylation step. A portion or all of this stream may be passed to the dehydrogenation step by being'passed from pipe |50 through pipe |55 and valve |56 to pipe I0. If desired, this stream may be discharged from the system through pipe |51 and valve |58. Any light hydrocarbons which it is desired not to have retained in the system may be discharged from the top of fractionator |40 through pipe |60 and valve IBI. When the initial charge to the dehydrogenation step, entering the system through pipe |0, is comprised predominantly of isoparaiiins such as isobutane, this material may also be used as a part or all of the fresh isoparailin charge to lthe alkylation. step. In such a case a portion of the stream entering the system through pipe l0 may be passe'd from this pipe through pipe 98 and'valve 99 to pipe 1 |50 and is passed by pump |52 to the alkylation step.

When isopentane is a part of the hydrocarbon material charged to the acid alkylation step and is present in excess so that an appreciable portion passes through this step unreacted, a part or all of this unreacted isopentane may be retained in the alkymer fraction removed through pipe |43, and at times a part may also be recycled to this step through pipe |50, pump |52 and pipe |53 and ||0, as is readily understood. Isopentane in itself is a valuable ingredient of premium motor fuels. Its introduction to the alkylation step thus produces a fuel having a desirably wide boiling range and having a good volatility. A combination motor fuel having a high .antlknock rating may be formed by blending the material produced in the polymerization step with the fuel discharged from the alkylation step. This may be accomplished by passing oil or any part of the fuel :lowing through pipe 46, through pipe and 'valve |66, and mixing it with a stream withdrawn fromA pipe |43 through pipe |61 and valve |68, with suitable control of valves 41 and |44. Both these streams comprise motor fuel hydrocarbons having high antiknock qualities, and since one, the alkymer, isparafilnic and the other, the polymer, is olenic, the resultant blend will be quite high as to antiknck value or octainenumber, since the blending octane number of the oleilnic component when blended with a parafnic stock, is not infrequently much lhigher than the octane number of the oleilnic duce an ellluent stream containing about 20 molk per cen-t of gaseous oleiins which were about half isobutene and half-lighter olefins predominantly propene.A All but a negligible fraction of the material lower boiling than propene wasremoved from this dehydrogenation effluent, a portion of unreacted propene was added as a recycle stock, and the mixture was passed under a pressureof about 1410 pounds per square inch over a granular silica-alumina catalyst at a temperature between 300 and 475 F. for a period sufficient to convert over of the isobutene in the charge to polymers, about 50% of the total propene in the charge also entered into the reaction producing some interpolymers such as isoheptenes with the isobutene. The normally liquid hydrocarbons, that is, the polymer fraction, Was readily separated from the butanes and lighter portion of the effluent. About one-third of this polymer had more than eight carbon atoms per molecule, and about one-eighth of it was too heavy to be included in a motor fuel having an end-point of 400? F. The normally gaseous fraction'separated from the polymers consisted of C: and C4 hydrocarbons, which was readily separated by fractionation into a saturated part containing about 2% olens and over 95% isobutane, and an unsaturated part containing about 40% propene. A

portion of this latter fraction was returned to the polymerization step as recycle stock,

The polymer material was separated by fractionation into two parts, one boiling below about 360 F. constituting about 82 per cent of the total polymer. This material, after being saturated by non-destructive hydrogenation, is a premium blending stock for aviation fuel having an octane number of about 91 and a high response to the addition of an antiknock agent such as tetraethyl lead. The second`portion-contained the higher boiling polymers and, although a. substantial portion would have been included in a gasoline having a higher end-point, such as about 400or F., such a fraction is considered as a higherboiling polymer fraction for the purpose of this Specification. y This liquid higher-boiling polymer fraction is blended 'with approximately an equal liquid volume of the light unsaturated, unreacted hydrocarbons mentioned above, and the combined stream is mixed with about 4 liquid volumes of the above mentioned isobutane fraction. The combined hydrocarbon stream. as a liquid, is continuously and intimately mixed with C6 per cent sulfuric acid in a ratio of about 1:2 and passed to a reaction chamber provided with means for maintaining a continuous agitation of the contents. The mixture is maintained, with removal of heat. at a temperature between about G and 100 F. for a reaction period of 5 to 20 minutes and is then passed to a separator to separate the hydrocarbon phase from the acid phase. the acid phase being recirculated to the reaction zone. Unreacted isobutane is readily separated from the hydrocarbon phase and i.; passed to the dehydrcgenation step. The remaining hydrocarbon fraction, after being neutralized with caustic alkali, is distilled to produce an aviation gasoline boiling below 330 F. which is over 95 per cent saturated and comprises isoparafiln hydrocarbons. The octane number (A. S. T. M, motor method) is about 89.

As a modification of the above example, isopentane equal to about of the isobutane charged to the acid alkylation step is added to the hydrocarbon mixture charged to this step. A part of this isopentane enters into the alkylation reaction, and the unreacted portion is retained in the finall gasoline product, thusproviding a product the Engler distillation curve of which has a more gradual rise than the product of the first example.

As ,previously mentioned the dehydrogenation step should be conducted at a pressure below about 200 pounds per square inch and may be either thermal or catalytic or a combination of both. Thermal dehydrogenation is preferably carried out between about 1000 and 1250 F., and catalytic dehydrogenation may be carried out between about 850 and 1100 F. In a combination of both, the thermal dehydrogenation should precede the catalytic. It has been found that the most desirable catalysts comprise or consist of chromium oxide, preferably the black, unglowed variety. -Suitable modifications are disclosed in U. S. Patents 1,905,383 and 2,098,959, and in the copending applications Serial Numbers 113,091 of Morey (now Patent 2,288,320, granted June 30, 1942), 173,708 of Matuszak et al. (now Patent 2,294,414, granted September i. 1942), 173,709 of Morey et al., and 263,000 of Schulze (now Patent 2,291,581, granted July 28, 1942) The polymerization step. while it may be thermal or catalytic, is preferably a catalytic one carried out in the presence of solid granular catalysts. A preferred catalyst is a silica-alumina catalyst, such as described in U. S. Patents 2,142,324 or 2,147,985; or a catalyst of somewhat similar properties may be prepared by intimately mixing an acidic hydrous silica Jelly and hydrous alumina jelly, preferably with the latter being present only to an extent of about l to 5% by weight, and subsequently drying and granulating the resultant material. As mentioned, other solid catalysts may be used. The pressure will generally be at least 200 pounds per square inch and need not be in excess of about 2000 pounds per square inch. Pressures sufficient to insure a substantially liquid phase operation are the most desirable, as brought out in the copending application Serial No. 747,964, now U. S. Patent 2,198,937, granted April 30, 1940, of which I am a coinventor. The temperature should be between 100 and 600 F.. with the most usual operation between 250 and 550 F. The vtemperature and reaction time are interdependent. and With either one fixed the other can be varied as necessary to give a more or less constant or steady polymerization of the oleflns.

The alkylation step, while it may be by any one of several known methods. is preferably carried out in the presence of a concentrated sulfuric acid or its equivalent, since it has been found that a much more desirable yield of gasoline range products will result when this agent is used. By concentrated sulfuric acid is meant acid having a concentration greater than per cent, and generally greater than per cent. At times a concentration greater than per cent, as with fuming sulfuric acid, may be desirable, especially with low reaction temperatures. Pressures required to hold the reactants in the liquid phase need not exceed about 100 pounds per square inch as a rule, and the temperature should not be in excess of about 100 F., and may be as low as about 0 F. The ratio of isoparamn to olefin should be at least 1:1, and is preferably higher, such as between 2:1 and 5:1 by volume. The higher ratios are especially desirable when the olefin is predominantly of higher molecular weight. The volume ratio of hydrocarbon to acid may be between about 1:3 and 5:1, and it is important that they be intimately admixed and emulsiied. Generally, with extremely thorough intermixing, this ratio may be in the upper part of the range. It has been found that a continuous intermixing of the reactants can be readily accomplished by passing them through a centrifugal pump and then through an elongated tube of a cross section sufficiently restricted to insure a rapid linear turbulent flow. This arrangement also affords a convenient method for removing the heat of reaction, as such a tube coil is readily surrounded by a heat-exchange medium.

I claim:

1. A process for the production of premium aliphatic hydrocarbons boiling in the motor fuel range from isobutane, which comprises dehydrogenating isobutane to produce isobutane and a substantial portion o1' propene, subjecting a hydrocarbon fraction containing isobutene and propene so produced, together with unreacted isobutane, to a catalytic polymerization under polymerization conditions such as to polymerize only a portion of the propene and substantially all of the isobutene to form olefin polymers boiling in and above the motor fuel range, passing the polymerization effluent to separating means, separating therefrom a fraction comprising olefin polymers boiling in the motor fuel range and removing same from the process as a product thereof, separating also a fraction comprising higher boiling polymers, a fraction comprising unreacted isobutene, and a fraction comprising unreacted propene, passing through an elongated reaction zone a stream comprising an intimate liquid mixture of a sulfuric acid alkylation catalyst and said isobutane fraction and said heavy polymer fraction, removing heat from said mixture in said zone during a, reaction period to maintain an alkylation temperature, adding at a plurality of points along the length of said reaction zone said propene fraction to supply additional olefin reactant to said zone and in amounts such as to maintain a relatively low olefin concentration, and recovering from an eiiluene of said zone a hydrocarbon fraction containing parafiins boiling in the motor fuel range so produced.

- 2. A process for alkylating a paraiin hydrocarbon of four to ve carbon atoms per molecule to produce isoparailins boiling in the motor fuel range, which comprises passing a stream comprising an intimate, liquid admixture of such an isoparaiiln, concentrated sulfuric acid and olen polymers boiling above the motor fuel range through an elongated reaction zone under alkylating conditions to produce isoparailins in the motor fuel range, adding at a plurality of points subsequent to the inlet of and along the length of said reaction zone a normally gaseous olefin of at least three carbon atoms per molecule to supply additional olen reactant to said zone and in amounts such as to maintain a relatively low olen concentration in said reaction zone, and recovering from an eiluent of said reaction zone a hydrocarbon'fraction containing isoparailns boiling in the motor fuel range so produced.

low-boiling iso- 3. A process for reacting a low-boiling isoparamn with low-boiling oleflns and oleiin polymers, which comprises passing a stream comprising an intimate liquid mixture of a sulfuric acid alkylation catalyst and a low-boiling isoparafiln and normally liquid olefin polymers through an elongated reaction zone under alkylating conditions to produce isoparafiins in the motor fuelrange. adding at least one point subsequent'to the inlet of and along the length of said reaction zone a normally gaseous olefln to supply additional olefin reactant to said zone and in amounts such as to maintain a relatively low olefin concentration in said reaction zone, and recovering from an eiliuent of said zone a hydrocarbon fraction containing isoparaiiins boiling in the motor fuel range so produced.

FREDERICK E. FREY.

e CERTIFICATE 0F crolmEc'lIiN'.` Patent No. 2,527,655. August 21+, 19M.'4

FREDERICK E. am.

page 6, se'cond column; line 9, for ."addf aho'uld be -rad with this gorect'on therein' that the same may lConforml to um. record of the case 11i-the Patent oramai,

C 'signed and sealed m1545011; day .of Novembe, Af., D. 1915;.. 

